Low profile stator adjusting mechanism



July 29, 1969 c, BURGE ET AL 3,458,118

LOW PROFILE STATOR ADJUSTING MECHANISM Filed Aug. 21. 1967 2 Sheets-Sheet 1 lfflit il July 29, 1969 J. c. BURGE ET AL LOW PROFILE STATOR ADJUSTING MECHANISM 2 Sheets-Sheet 2 Filed Aug. 21, 1967 United States Patent 3,458,118 LOW PROFILE STATOR ADJUSTING MECHANISM Joseph C. Burge and Richard W. Follmer, Cincinnati,

Ghio, assignors to General Electric Company, a corporation of New York Filed Aug. 21, 1967, Ser. No. 662,009 Int. Cl. F04d 27/00, 25/02 US. Cl. 230-414 12 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a variable geometry system for an axial flow compressor of the type used in gas turbine engines and, more particularly, to a stator adjusting mechanism particularly adapted for use in limited space applications.

Axial flow compressors of the so called variable geometry or adjustable stator type have been found highly effective for pressurizing air to support combustion in gas turbine engines, particularly where such engines are used for the propulsion of aircraft. Compressors of the type referred to comprise a casing and a rotor having stator vanes and rotor blades mounted respectively thereon. The stator vanes and rotor blades are disposed in alternate circumferential rows, with each adjacent pair of rows forming a compressor stage. The blades and vanes are disposed generally radially of the rotor with the stator vanes of at least the initial stages being pivotal about these radial axes.

By adjusting the pivotally mounted stator vanes about such radial axes, it has been found that highly efiicient operation of the compressor can be obtained. In making such adjustments it is usually essential that all stator vanes of a given stage be pivoted simultaneously and to the same extent. Where more than one stage of stators are varied, it is usually essential that all stages be adjusted simultaneously, but not necessarily to the same angular extent.

In gas turbine engines of the front fan type in which the front fan discharges a portion of its air flow to an axial flow compressor and the remainder of its air flow to an annular bypass passage surrounding the compressor, the space between the compressor casing and the inner wall of the bypass passage is often very limited in radial height. It has been found that adjusting mechanism used heretofore for adjusting the angular positions of compressor stator vanes can not be fitted into the limited space available in some front fan engines.

It is therefore an object of this invention to provide a low profile stator adjusting mechanism.

Another object of this invention is to provide for front fan gas turbine engines a stator adjusting mechanism having a low profile for use in the annular space between the .compressor and the bypass passage.

Still another object of the present invention is to provide for variable geometry systems of gas turbine engines an improved stator mechanism that is both lightweight and compact.

A further object is to provide a low profile stator adjusting mechanism not only having the characteristics enumerated above, but also being rugged and simple in construction and operation.

Patented July 29, 1969 Briefly stated, in carrying out the invention in one form, an axial flow compressor having at least two rows of variable stator vanes includes a stator adjusting mechanism comprising axially spaced-apart actuating rings ganged together in fixed relative positions for equal and simultaneous rotation about the compressor and axially disposed actuation means connected to an end ring only for rotating the actuating rings. The actuating rings are connected to the stator vanes of respective rows such that rotation of the rings causes corresponding movement of the variable stator vanes. More particularly, the actuation means includes a suitable mechanism, such as a bellcrank, for converting axial movement of a force producing device, such as a hydraulic actuator, into circumferential movement of the actuating rings. The unique axial configuration of the stator adjusting mechanism makes possible a low radial profile suitable for use in regions of limited radial height.

By still further aspects of the invention, the structure interconnecting the actuating rings includes means for permitting adjustment of the fixed relative positions of the rings so that the relative angular positions of the rows of vanes can be selectively varied, and the various components are universally connected to permit free movement in various planes.

While the novel features of this invention are set forth with particularity in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description when taken in conjunction with the drawings, in which:

FIG. 1 is a view partially in cross section of a gas turbine engine of the front fan type, the engine having the stator adjusting mechanism of this invention;

FIG. 2 is an enlarged view, also partially in cross section, of the axial flow compressor of the engine of FIG. 1;

FIG. 3 is a view taken along viewing line 33 of FIG. 2; and

FIG. 4 is a view taken along viewing line 4-4 of FIG. 2.

Referring first to FIG. 1, a gas turbine engine 10 of the front fan type is illustrated, the engine 10 including an axial flow fan 12, a core engine 14, and a bypass passage 16 surrounding the core engine 14. More particularly, the front fan 12 communicates at its upstream end with an inlet 18 and at its downstream end with the bypass passage 16 and an annular inlet 20 to the core engine 14, the air flowing through the front fan 12 during engine operation being divided into a bypass stream received by the bypass passage 16 and a combustion supporting portion received by the annular inlet 20. The bypass stream is discharged to atmosphere through an annular outlet 22 at the downstream end of the bypass passage 16 to produce thrust. The air supplied to the annular inlet 20 and the core engine 14 is compressed by an axial flow compressor 24 to provide the proper air pressure for supporting combustion of fuel within an annular combustor 26. The combustion products are then supplied to a high pressure turbine 28 where energy is extracted for driving the axial flow compressor 24 through a hollow shaft 30 and a low pressure turbine 32 where energy is extracted for driving the front fan 12 through a shaft 34 coaxially disposed within the shaft 30. After driving the turbines 28 and 32, the combustion products are discharged to atmosphere through an outlet 36 to produce thrust. The total engine thrust is thus provided by the bypass stream flowing through the outlet 22 in combination with the combustion products flowing through the outlet 36.

Referring now to FIGS. 1 and 2, it will be noted that the inner wall 38 of the bypass passage 16 and the casing 40 of the axial flow compressor 24, cooperate to form an annular region 42 within which various engine accessories, such as a stator adjusting mechanism 44, may be located. Depending upon the bypass ratio, which is the ratio of the air flow through the bypass passage 16 in pounds to the air flow to the core engine 14 in pounds, and other design considerations, the annular region 42 can vary substantially in size. In the illustrated engine, the bypass ratio is 1.4 to 1, and the inner wall 38 of the bypass passage 16 and the casing 40 of the compressor 24 are closely spaced such that the space 42 has a very limited radial height R. More particularly, the annular space 42 in the illustrated engine has a maximum radial height of only 12.5 inches. It will occur to those skilled in the art that the bypass passage 16 could be turned outwardly to increase the radial height R if necessary to accommodate the engine accessories; however, this approach would adversely affect the aerodynamics of the bypass stream and increase the frontal area, the aerodynamic drag, and possibly the weight of the engine 10.

Turning attention now to FIG. 2, the axial flow compressor 24 incudes a plurality of axially spaced-apart rows 48, 50, 51, etc., of radially disposed and circumferentially spaced stator vanes, the first two rows 48 and 50 being of the variable geometry type to accommodate different conditions during engine operation. To provide the variable geometry, each vane 52 of the upstream row 48 has a stub shaft 54 at its outer end which is journaled by appropriate means in the compressor casing 40, and each vane 56 of the second row 50 has a stub shaft 58 also journaled by appropriate means in the casing. The vanes 52 and 56 are also appropriately journaled at their inner ends by means not shown. In response to changing engine operating conditions, it is desirable that the vanes 52 and 56 be simultaneously adjusted through selected angles about their respective stub shafts 54 and 58, the axes of which are radial of the engine axis. More specifically, all of the vanes 52 should be rotated simultaneously through a common angle, and all of the vanes 56 should be rotated simultaneously through a common angle, but the vanes 52 and 56 need not be rotated through the same angle. To provide such movement, the novel stator adjusting mechanism 44 of this invention is provided in the limited space 42.

Referring now to FIGS. 2-4, the stator adjusting mechanism 44 inches a first actuating ring 60 surrounding the compressor casing 40 in proximity thereto between the rows 48 and 50 of stator vanes and a second actuating ring 62 surrounding the casing 40 axially downstream of the row 50 of vanes. A plurality of relatively thin levers 64 are secured to the stub shafts 54, each lever 64 being disposed in a plane substantially normal to the axis of the respective stub shaft 54 and extending downstream of the stub shaft 54 in a generally axial direction to the first ring 60 to which it is pivotally connected about an axis radial of the engine axis by means 65 described hereinafter in greater detail. So that circumferential movement of the actuating ring 60 will result in equal rotation,

of all of the vanes 52, the levers 64 are all of the same length. Similarly, a plurality of equal-length levers 66 are secured to respective stub shafts 58 and extend axially therefrom to the second actuating ring 62 where they are pivotally mounted by means 68. To provide simultaneous adjustment of the two rows 48 and 50, the rings 60 and 62 are ganged together by an axially disposed bracket 70 which holds the rings in fixed relative positions so that given circumferential rotation of one ring about the engine axis will cause equal rotation of the other actuating ring. While only one bracket 70 is illustrated, it will be understood that a more stable mechanism will be provided by at least two brackets on opposite sides of the compressor casing 40. By careful selection of the lengths of the levers 64 and 66, equal rotation of the rings 60 and 62 can result in equal or unequal adjustment of the stator vanes 52 and 56.

To drive the actuating rings 60 and 62, an actuation system 72 is provided axially downstream of the second ring 62, the actuation system including a bellcrank 74 pivotally mounted at 76 on the casing 40 downstream of the second ring 62. The bellcrank 74 includes a first arm 78 projecting axially upstream of the pivotal connection 76 into overlying relationship with the second ring 62 and a second arm 80 projecting tangentially from the pivotal connection 76 at right angles to the first arm 78. The upstream end of the first arm 78 is connected to the second ring 62 by a link 82 for converting oscillation of the bellcrank 74 in its tangential plane into circumferential rotation of the rings 60 and 62. To move the bellcrank 74 and thereby adjust the rings 60 and 62 and the vanes 52 and 56, a hydraulic actuator 84 is connected to the end of the second arm 80 and to the compressor casing 40 axially downstream of the bellcrank 74, Other drive means such as a mechanical screw and jack arrangement could, of course, be used in the practice of the present invention to drive the stator adjusting mechanism 44. As in the case of the brackets 70, it will be understood that a more stable mechanism can be provided by at least two actuation systems 72 on opposite sides of the compressor casing 40.

In the foregoing description, it has been pointed out that the vanes 52 of the first row 48 are set at a common angle at all times, any common adjustment occurring simultaneously for all vanes 52. The vanes 56 of the second row 50 are likewise set at a common angle at all times and are adjusted simultaneously. Furthermore, both rows 48 and 50 of vanes are adjusted simultaneously by the stator adjusting mechanism 44, but not necessarily through the same angles. However, as described, there is a direct correlation at all times betwen the positions of the vanes 52 and 56 since the actuating rings 60 and 62 are ganged together for movement in concert. To provide greater flexibility, the bracket 70 is formed of a first portion 86 rigidly attached to the first ring 60 and a second portion 88 connected to the second ring 62 by a universal type spherical connector 90, the two portions 86 and 88 being connected by bolts 92 projecting through slots 94 in the second portion 88 for permitting relative circumferential movement between the two rings 60 and 62 to selectively adjust their fixed relative positions. Thus, by loosening the bolts 92 and moving the two rings 60 and 62 relative to each other, the angular relationship of the vanes 52 with respect to the vanes 56 can be varied for any particular setting of the actuation system 72.

A stator adjusting mechanism 44 such as that described herein includes a number of elements moving in various paths. For example, the levers 64 and 66 move in planes normal to the axes of the respective stator vanes and the rings 60 and 62, to which the levers 64 and 66 are pivotally connected by means 65 and 68, move in circular paths around the compressor casing 40. To permit such movement without binding, the means 65 and 68 include, as best illustrated by FIG. 4, inserts 96 in the rings 60 and 62 and pins 98 secured to the downstream ends of the levers 64 and 66, the pins 98 being slidably received in the inserts 96. In opeartion, movement of the rings 60 and 62 will either cause the thin levers 64 and 66 to flex slightly, or the pins 98 to ride radially out of the inserts 9, or the inserts 96 to shift slightly in the rings 60 and 62. Similarly, the link 82 connected at 100 to the first arm 78 of the bellcrank 74 and at 102 to the second ring 62, the connection 100 being constrained to movement in a plane tangential to the compressor casing 40 and the connection 102 being constrained to circular movement about the casing 40. To permit such movement without binding, the connections 100 and 102 are of the spherical type for providing universal movement. Similarly, the hydraulic actuator 84 includes connectors 104 and 106 of the universal type, and the bracket 70 is connected to the second ring 62 by a spherical connector 90. In addition to permitting movement without binding,

the universal type connectors used in the stator adjusting mechanism 44 may be clamped tight so as to provide precise movement without hysteresis.

From the foregoing, it will be appreciated that the stator adjusting mechanism 44 of this invention provides an extremely low radial profile since the various components are axially disposed without being radially overlapped, except for the ring 62 and the link 82 which could be partially offset axially if necessary. In addition, the adjusting mechanism 44 utilizesa minimum number of parts by using common drive means for driving both actuating rings, the result being not only a compact arrangement, but also a rugged and lightweight configuration.

Those skilled in the art will appreciate that the present invention could be used for selectively adjusting any number of rows of stator vanes, adjacent actuating rings being interconnected for movement in concert and the drive means being connected to an axially end one only of the actuating rings. Also, While the present invention is particularly adapted for use in front fan engines in which limited space is available between the compressor and the bypass passage, persons skilled in the art will appreciate that the invention is suited for use wherever the space available around the compressor is limited. Indeed, the simplicity, ruggedness, and low weight of the stator adjusting mechanism make it attractive for use in applications in which space is not particularly limited.

It will be understood that the invention is not limited to the specific details of the construction and arrangement of the particular embodiment illustrated and described herein. It is therefore intended to cover in the appended claims all such changes and modifications which may occur to those skilled in the art without departing from the true spirit and scope of the invention.

What is claimed as new and is desired to secure by Letters Patent of the United States is:

1. In an axial flow compressor including a generally cylindrical casing and axially spaced-apart circumferential rows of stator vanes mounted therein for pivotal movement about axes radial of the axis of the compressor, a stator adjusting mechanism comprising:

a plurality of axially spaced-apart actuating rings circumferentially surrounding the compressor casing, each actuating ring being oifset axially from a respective row of pivoted stator vanes,

a plurality of relatively thin levers each secured to a respective stator vane outwardly of the compressor casing and extending axially therefrom to the respective actuating ring in a plane substantially normal to the axis of the stator vane,

means pivotally connecting each of said levers to the respective actuating ring about an axis substantially radial of the axis of the compressor,

at least one bracket extending axially between and interconnecting each adjacent pair of actuating rings in fixed relative positions such that circumferential rotation of one of said rings about the axis of the compressor results in equal rotation of the other actuating rings, each said bracket being rigidly secured at its one end to one of said actuating rings and connected at its other end to a ring adjacent said one actuating ring,

and at least one actuation means connected to an axially end one only of said actuating rings for directly rotating said end actuating ring, thereby indirectly rotating the other actuating rings through said interconnecting means and causing corresponding pivotal movement of the stator vanes,

said actuation means extending away from said actuatings rings in a generally axial direction to minimize the radial height of the stator adjusting mechanism.

2. A stator adjusting mechanism as defined by claim 1 in which said actuation means comprises:

a bellcrank having first and second arms disposed at right angles to each other,

means at the intersection of said first and second arms pivotally mounting said bellcrank to the compressor casing for permitting movement of said arms in a plane substantially tangential to the casing, said pivotal mounting means being axially spaced from said end actuating ring,

said first arm projecting from said pivotal mounting means toward said end actuating ring in a generally axial direction,

a link interconnecting said first arm at a point remote from said pivotal mounting means to said end actuating ring for converting movement of said bellcrank into corresponding circumferential movement of said actuating rings,

and drive means connected to said second arm at a point remote from said pivotal mounting means for oscillating said bellcrank within said tangential plane,

said drive means extending away from said bellcrank and said actuating rings in an axial direction.

3. A stator adjusting mechanism as defined by claim 2 in which said bracket between adjacent actuating rings includes ameans for varying the fixed relative positions of said actuating rings so that the relative angular positions of the rows of vanes can be selectively varied.

4. A stator adjusting mechanism as defined by claim 3 in which said drive means comprises a hydraulic actuator connected at opposite axial ends to said second arm and the compressor casing.

5. A stator adjusting mechanism as defined by claim 4 in which the means pivotally connecting said vane positioning levers to the respective rings permits limited movement between the levers and the actuating rings along the pivotal axes, said stator adjusting mechanism further including connecting means of the universal type between said link and said first arm and said end actuating ring.

6. A stator adjusting mechanism as defined by claim 5 further including connecting means of the universal type between said bracket and at least one of said adjacent actuating rings.

7. In a turbofan engine including a front fan and an axial flow compressor located downstream of the front fan for receiving a portion of the air flow through the front fan, the remainder of the air flow through the front fan being discharged through an annular bypass passage surrounding the compressor, the compressor having a generally cylindrical casing and the bypass passage having a generally cylindrical inner wall member which cooperate to forman annular region of limited radial height, a variable geometry system comprising:

a first circumferential row of peripherally spaced-apart stator vanes in said compressor, each of said vanes being mounted for pivotal movement about an axis radial of the axis of the compressor; second circumferential row of peripherally spacedapart stator vanes in said compressor axially downstream of said first row, each of said vanes being mounted for pivotal movement about an axis radial of the axis of the compressor; and a stator adjusting mechanism comprising:

a first actuating ring circumferentially surrounding said compressor casing, said first actuating ring being located in said region of limited radial height axially intermediate said first and second rows of stator vanes and being mounted for rotation about said casing, second actuating ring circumferentially surrounding said compressor casing, said second actuating ring being located in said region of limited radial height axially downstream of said second row of stator vanes and being mounted for rotation about said casing,

a plurality of relatively thin levers each secured to a respective stator vane outwardly of the compressor casing and extending axially therefrom to the respective actuating ring in a plane substantially normal to the axis of the stator vane,

means pivotally connecting each of said levers to the respective actuating ring about an axis substantially radial of the axis of the compressor,

means extending axially between and interconnecting said first and second actuating rings in fixed relative positions such that circumferential rotation of one of said rings about the axis of the compressor results in equal rotation of the other actuating ring,

and a pair of actuation means connected to said second actuating ring for simultaneously and directly rotating said second actuating ring, thereby indirectly rotating said first actuating ring through said interconnecting means and causing corresponding pivotal movement of the stator vanes of said first and second rows,

said actuation means being disposed on diametrically opposite sides of said compressor casing and each extending axially downstream of said second actuating ring,

whereby said stator adjusting mechanism is axially disposed for minimum radial height so as to fit within said region of limited radial height.

8. A variable geometry system as defined by claim 7 in which each of said actuation means comprises:

a bellcrank having first and second arms disposed at right angles to each other,

means at the intersection of said first and second arms pivotally mounting said bellcrank to the compressor casing for permitting movement of said arms in a plane substantially tangential to the casing, said pivotal mounting means being axially spaced downstream of said second actuating ring, said first arm projecting axially upstream from said pivotal mounting means with its upstream end overlying said second actuating ring,

a link universally interconnecting the upstream end of said first arm and said second actuating ring for converting movement of said bellcrank into corresponding circumferential movement of said actuating rings, and

drive means universally interconnecting said second arm at a point remote from said pivotal mounting means and said casing at a point axially down-stream of said second arms for oscillating said bellcrank within said tangential plane.

9. A variable geometry system as defined by claim 8 in which said interconnecting means between said first and second actuating rings includes means for varying the fixed relative positions of said actuating rings so that the relative angular positions of the rows of vanes can be selectively varied.

10. A variable geometry system as defined by claim 9 in which said drive means comprises a hydraulic actuator.

11. A variable geometry system as defined by claim 10 in which the means pivotally connecting said vane positioning levers to the respective rings permits limited movement between the levers and the rings along the pivotal axes.

12. A variable geometry system as defined in claim 11 further including connecting means of the universal type between said interconnecting means and at least one of said actuating rings.

References Cited UNITED STATES PATENTS 2,933,234 4/1960 Neumann. 2,955,744 10/ 1960 Hemsworth. 2,999,630 9/1961 Warren et a1. 3,146,585 9/ 1964 Gulick. 3,314,595 4/ 1967 Burge et al. 3,352,537 11/1967 Petrie. 3,360,240 12/ 1967 Williamson et a1. 3,376,018 4/1968 Williamson.

HENRY F. RADUAZO, Primary Examiner US. Cl. X.R. 230-116 

